Y. Tokumaru, et al., "I.sup.2 L with Self-Aligned Double Diffused Injector", 1976, IEEE Solid State Conference, pp. 100-101, shows in FIG. 5 a lateral PNP transistor and vertical NPN transistor formed in a P-type epitaxial layer, the base of the NPN transistor is the epitaxial layer itself. This is a typical low cost, low performance structure for complementary bipolar devices which suffers from the relatively wide tolerances in the thickness of the epitaxial layer and consequent wide variations in the performance of the NPN device. The subject disclosure improves upon this prior art structure by forming the base of the vertical NPN and the collector on the lateral PNP as a diffused or ion-implanted region in an N-type epitaxial layer, during the same step. The base thickness of the NPN device is therefore no longer dependent upon the thickness of the epitaxial layer and the simultaneous formation of the PNP and the NPN attributes to an economic, efficient process. The base-collector capacitance of the lateral PNP device in the subject disclosure is reduced with respect to the prior art structure, since the concentration of the N-type epitaxial region surrounding the collector and which serves as the extrinsic base is relatively low.
U.S. Pat. No. 3,977,920 suffers from the same deficiencies as does the Tokumara publication.